1. Field of the Invention
This invention relates to a machine for bending a small-diameter metallic conduit at several points and more particularly, to a small-diameter metallic conduit bending machine adapted to shape a metallic conduit whose individual bend portions differ in the bend direction from one another three-dimensionally, not lying on the same plane, such as the fuel pipeline or brake pipeline of a car.
2. Description of the Prior Art
A conventional bending machine of the foregoing type includes a required number of simple bending units corresponding to the number of bend portions, each unit being configured as shown in FIG. 13 so that with respect to one bending process, a receiving roll 11 is first moved by a cylinder 12 to come into contact with a metallic conduit 13, and then a bending roll 14 is moved by a cylinder 15 to bend the metallic conduit 13. In the drawing, 16 and 17 are mounts, 18 and 19 are stays, and 20 is a base.
According to the foregoing conventional bending machine, however, since the bending process is carried out by moving the receiving roll 11 and the bending roll 14 by means of the respective cylinders 12 and 15, one bending process needs two actions; thus, the processing time is long. Since the bending process is completed when the piston rods of both cylinders 12 and 15 are in an extended state, upon supply of a pressurized fluid into the cylinder (generally, an air cylinder) at the time of bending, the bending moment imposed on the piston rod increases, and flexure resulting from the reaction caused at the time of bending appears in the stays 18 and 19 and mounts 16 and 17 for supporting the cylinders 12 and 15; as a result, a minute discrepancy (called "breathing" by those skilled in the art) occurs between the receiving roll 11 and the bending roll 14, thereby resulting in variations in products. To eliminate such a discrepancy, it is necessary to make the stays 18 and 19 and the mounts 16 and 17 thick and rigid; consequently, the machine becomes large in size and heavy in spite of such provisions however, some discrepancy cannot be removed. Further, since the whole machine is designed and composed while giving consideration to the position, orientation, etc. of each of the cylinders 12 and 15, receiving roll 11 and bending roll 14, a long time is needed for manufacture, such as assembly and adjustment; as a result, the machine cannot be put in service in time where the start of mass production is settled. In addition, since the number of parts and of moving portions is large, the manufacturing cost is very high and the durability is inferior.